The present invention relates to a process for preparing 2,4-dichloro-5-hydroxyacetanilide, said process being an advance on the prior art.
2,4-Dichloro-5-hydroxyacetanilide is an important intermediate in the preparation of crop protection agents (WO 85/01939).
2,4-Dichloro-5-hydroxyacetanilide can be prepared by chlorination of 3-hydroxyacetanilide, which is obtainable by acetylation of 3-aminophenol.
The reaction of 3-hydroxyacetanilide with gaseous chlorine in glacial acetic acid described in WO 86/00072 on page 25 under Example III Step B leads to a yield of only 30.4% of theory, based on 3-hydroxyacetanilide employed.
With reference to Example 2 Step B, WO 85/01939 describes, on page 27 under Example 3 Step B, the reaction of 3-hydroxyacetanilide with sulfuryl chloride in glacial acetic acid. According to the specifications on page 25 Example 2 Step B, in the preparation of 2,4-dichloro-5-methylacetanilide, the reaction mixture is, after the addition of sulfuryl chloride to 3-acetamidotoluene, allowed to stand at room temperature for approximately 60 hours and subsequently heated, until a stirrable material is formed, and then stirred for approximately 5 hours more. The 2,4-dichloro-5-hydroxyacetanilide prepared in accordance with Example 3 Step B in a similar manner to Example 2 Step B is obtained in a yield of 43.5%, based on 3-hydroxyacetanilide employed.
The yields of 2,4-dicholor-5-hydroxyacetanilide obtained in the two examples described above are comparatively low, and the processes are therefore not to be recommended for industrial realization.